Shutdown for an ink jet printer

Abstract

A system and method are provided for improving the reliability for shutting down high resolution ink jet printheads for continuous ink jet printers. The shutdown technique fo the present invention solves the problem of ink and/or flush fluid drying in or around orifice holes on higher resolution printheads. This is accomplished with pulse modulation of air pressure used to blow and dry the printhead filters while balancing air flow and negative pressure across the droplet generator and the orifice array.

What is claimed is:  
     
       1. A method for shutting down printheads of a continuous ink jet printing system having a droplet generator with an inlet and an outlet, an associated orifice plate, a jet array, a charge plate, and a catcher, the method comprising the steps of: 
       providing means to supply vacuum to the outlet of the droplet generator to remove ink from the droplet generator;  
       providing means to supply clean, pressurized air to the inlet of the droplet generator to assist in removal of ink from the droplet generator; and  
       pulsing at least one of the supply means to supply vacuum or supply pressurized air such that when both supply means are active, resultant high air flow rate through the droplet generator removes fluid from the droplet generator, and when one of the supply means is inactive, a zero pressure region along the orifice array is eliminated.  
     
     
       2. A method as claimed in  claim 1  wherein the step of pulsing at least one of the supply means comprises the step of pulsing the means to supply clean, pressurized air while providing a constant supply of vacuum to the outlet of the droplet generator. 
     
     
       3. A method as claimed in  claim 1  wherein the step of providing means to supply clean, pressurized air comprises the step of pulsing an air supply pump. 
     
     
       4. A method as claimed in  claim 1  wherein the step of providing means to supply clean, pressurized air further comprises the step of providing valve means to stop flow of air to the inlet of the droplet generator. 
     
     
       5. A method as claimed in  claim 1  wherein the step of pulsing at least one of the supply means comprises the step of pulsing the means to supply vacuum while providing a constant supply of clean pressurized air to the inlet of the droplet generator. 
     
     
       6. A method as claimed in  claim 1  wherein the step of providing means to supply vacuum to the outlet of the droplet generator further comprises the step of pulsing a vacuum pump. 
     
     
       7. A method as claimed in  claim 1  wherein the step of providing means to supply vacuum further comprises the step of providing valve means to isolate the outlet of the droplet generator from the vacuum. 
     
     
       8. A method as claimed in  claim 1  wherein the step of pulsing further comprises the step of substantially drying and removing fluid from the droplet generator and the jet array. 
     
     
       9. A system for shutting down printheads of a continuous ink jet printing system having a droplet generator with an inlet and an outlet, an associated orifice plate, a jet array, a charge plate, and a catcher, the system comprising: 
       means to supply vacuum to the outlet of the droplet generator to remove ink from the droplet generator;  
       means to supply clean, pressurized air to the inlet of the droplet generator to assist in removal of ink from the droplet generator; and  
       means for pulsing at least one of the supply means to supply vacuum or supply pressurized air such that when both supply means are active, resultant high air flow rate through the droplet generator removes fluid from the droplet generator, and when one of the supply means is inactive, a zero pressure region along the orifice array is eliminated.  
     
     
       10. A system as claimed in  claim 9  wherein the means for pulsing at least one of the supply means comprises the means for pulsing clean, pressurized air while providing a constant supply of vacuum to the outlet of the droplet generator. 
     
     
       11. A system as claimed in  claim 9  wherein the means to supply clean, pressurized air comprises an air supply pump. 
     
     
       12. A system as claimed in  claim 11  wherein the air supply pump is pulsed. 
     
     
       13. A system as claimed in  claim 9  wherein the means to supply clean, pressurized air further comprises valve means to stop flow of air to the inlet of the droplet generator. 
     
     
       14. A system as claimed in  claim 9  wherein the means for pulsing at least one of the supply means comprises the means for pulsing the vacuum supply while providing a constant supply of clean pressurized air to the inlet of the droplet generator. 
     
     
       15. A system as claimed in  claim 9  wherein the means to supply vacuum comprises a vacuum pump. 
     
     
       16. A system as claimed in  claim 15  wherein the vacuum pump is pulsed. 
     
     
       17. A system as claimed in  claim 9  wherein the means to supply vacuum further comprises valve means to isolate the outlet of the droplet generator from the vacuum. 
     
     
       18. A system as claimed in  claim 9  wherein the means for pulsing further comprises means for substantially drying and removing fluid from the droplet generator and the jet array.